Moray S. Stark

Extraction and tribological investigation of top piston ring zone oil from a gasoline engine

Abstract With tightening emission regulations, increased expected fuel economy, and longer drain intervals impacting on lubricant formulation, greater understanding of how oil degrades in an automotive engine is becoming ever more important. Equally significant is the effect that this degraded lubricant has on the tribological operation of the engine, particularly its overall internal friction and component wear In a previous paper, four tests to degrade oil in a single cylinder engine were reported [1]. These tests were set up such that the lubricating oil was degraded in the ring pack before returning to the sump, where it was sampled and chemical and rheological analysis undertaken. This paper reports the extension of this work using the same Hydra engine and describes how oil has additionally been extracted from the rear of the top piston ring during engine operation. This extracted oil has then been subjected to similar analysis as the sump oil samples in the previous tests, along with additional analysis to look at the tribological properties of the oil using tribometers. The results clearly show significant differences in the rheological, tribological, and chemical properties of the fresh oil and used sump oil samples when compared with the top ring zone (TRZ) oil samples, particularly the effect of load on the levels of volatiles present in the TRZ samples and their effect on traction and friction coefficient values during tribological testing.

The degradation of lubricants in gasoline engines: Development of a test procedure to evaluate engine oil degradation and its consequences for rheology

Tests have been undertaken to study the effects of engine parameters and lubricant blends on oil degradation and engine components. A single cylinder spark ignition research engine was used for this work. The cam shaft was run on fully formulated oil and the crank and piston ring pack on the test oils. Samples were extracted from the sump, whilst the engine was running under controlled conditions, and rheological and chemical analysis data obtained from these samples. The methodology behind the testing and the engine set up is presented, as are results for the viscosity, sump carbonyl concentration and the end of test component condition for the four tests undertaken. Comparisons between the oil blends, engine parameters and results are discussed before conclusions are drawn and areas for further work highlighted.

Kinetic study of the reactions of tert-butyl radicals in the liquid phase in the presence and absence of oxygen

The photolyses of solutions of 2,2′-azoisobutane and 2,2,4,4-tetramethylpentan-3-one in decane in glass and metal cells, have been used to generate tert-butyl and, by reaction with oxygen, tert-butylperoxyl radicals. Time-dependent product yields from reactions in oxygenated and oxygen-free solutions have been measured over a range of temperatures (298–398 K). For each precursor, for a given set of conditions, the general features of the reactions are independent of the cell used, although the absolute rates of product formation are different. The major difference between the reactions of the two precursors lies in the initial photochemical step. For 2,2′-azoisobutane this leads directly to two tert-butyl radicals whereas the ketone gives a tert-butyl and a 2,2-dimethyl-propanoyl radical. The product distributions can be accounted for in terms of the reactions of these radicals within a solvent cage in competition with cage escape and subsequent reaction. A single kinetic model that accounts for the reactions of both precursors, in the presence or absence of oxygen, at the temperatures studied, is described.

Effect of spruce-derived phenolics extracted using microwave enhanced pyrolysis on the oxidative stability of biodiesel

An investigation has been carried out to characterize and evaluate phenolic compounds of bio-oils produced by the microwave enhanced pyrolysis of spruce woodchips (picea abies) for their potential application in stabilizing biodiesel from autoxidation. Four extracts were isolated from the bio-oil through multi-fractionation steps using a liquid–liquid extraction method: water-soluble, neutral, phenolic and organic acids extracts. The crude bio-oil and the isolated extracts were characterized by GC-MS, GC-FID, total phenols by Folin–Ciocalteu assay, ATR-IR and 13C NMR. The antioxidative effect of the crude bio-oil, its isolated extracts and two significant phenolic components (eugenol and catechol) of the crude bio-oil were also investigated using methyl linoleate as a biodiesel model by means of a high temperature (120 °C) oxidation test. The results show that methyl linoleate induction time increased after blending small amounts (1.4–5.6% w/w) of either the crude bio-oil or the isolated extracts. However, the crude bio-oil showed higher induction times in comparison with its isolated extracts, which was significant because the crude bio-oil contained a lower concentration of phenolic species (23% w/w), especially in comparison to the phenolic concentration in the phenolic extract (49.6% w/w). Furthermore, catechol was found to be very effective and was similar to crude bio-oil in the inhibition of methyl linoleate autoxidation, unlike eugenol, which was less effective at equivalent molar concentrations. Also, the effect of catechol and the crude bio-oil on methyl linoleate induction time was approximately comparable with a commercial antioxidant (butylated hydroxytoluene) when treated at equivalent molar concentration of phenols.

Lubricant Degradation Studies Using a Single Cylinder Research Engine

With increasing pressure on engine oil manufacturers to extend oil drain intervals and reduce fuel consumption, whilst changing the composition of fully formulated oils to meet new CEC, ILSAC and OEM specifications, there is ever increasing need to understand the effect of oil degradation on the operating conditions and tribological performance of engines. This poster presents mechanical changes made to a single cylinder research engine to enable the study of lubricant degradation, its transport and how this links to piston assembly tribology. A summary of the research undertaken using these changes and a sample of results obtained to date are also presented.Copyright

The formation of propene oxide from the co-oxidation of propene and acetaldehyde

Abstract Experiments have been conducted to seek ways to enhance the selectivity of propene oxide in the autoxidation of propene in the gas phase. The experiments were carried out in two systems, one static and the other a continuously stirred tank reactor, in order to obtain a wide range of conditions. The results reported in this paper have been obtained between 505 and 549K and pressures of 0.9 to 55 bar. Monitoring the perturbation in the product distribution shows that the selectivity of propene oxide is increased markedly on decreasing the temperature. Addition of acetaldehyde to propene: oxygen mixtures, by providing an additional source of peroxy radicals, enhances further the yield of epoxide to the extent that the process could be made commercially viable. Addition of formaldehyde was found not to increase the epoxide selectivity, as its oxidation does not provide an additional source of peroxy radicals. A previously published reaction scheme, constructed to model propene oxidation at low pressu...

A mechanistic study of the liquid phase autoxidation of nonan-5-one

The liquid phase autoxidation of nonan-5-one has been studied as a model for the degradation of ketones formed from the oxidation of lubricants in automotive combustion engines. The oxidation, at 120 °C, gives a large number of products (32 identified), including derivatives of the substrate with an intact carbon skeleton and low molecular mass compounds, from radical fragmentations, as well as carbon oxides. The products were identified and quantified by GC-MS and GC, with the characterisation of isomers being aided by measuring the deuterium content of products from the autoxidation of 4,4,6,6-[2H4]-nonan-5-one. Products arising from hydrogen atom abstraction from all the secondary C–H bonds were observed, with the main site of attack being α to the carbonyl group. The ketoalkyl, ketoperoxyl and ketoalkoxyl radicals formed in the reaction undergo radical dimerisation, disproportionation and hydrogen atom abstraction. With the ketoalkoxyl radicals the dominant pathway is β-scission, indeed ∼58% of the total product yield arises from this fragmentation of the α-ketoalkoxyl radical. Mechanisms for the formation of the observed products are proposed and used to determine the selectivity of the autoxidation for the different C–H bonds in the substrate.

The Tribological and Chemical Analysis of Top Ring Zone Samples of Fully Formulated Oil Taken From a Four Stroke Gasoline Engine

With increasing pressure on engine oil manufacturers to extend oil drain intervals and reduce fuel consumption, whilst changing the composition of fully formulated oils to meet the new CEC, ILSAC and OEM specifications, there is an ever increasing need to understand the effect of oil degradation on the operating conditions and tribological performance of engines [1]. This work samples oil from the rear of the top piston ring of an engine during the first 15 minutes from cold start and operating at steady state under three different loads. These samples, used 40 hour sump oil and fresh oil have been subjected to tribological tests and chemical analysis.Copyright